Prediction of recurrence based on the patellofemoral morphological profile and demographic factors in first-time and recurrent dislocators



Prediction of recurrence in first-time patellar dislocation is an unsolved mystery. The purpose of our study is to compare patellar instability patients and normal control groups with anatomical risk factors and validation of newer parameters patello-trochlear index (PTI) and tibial tuberosity-posterior cruciate ligament (TT-PCL) and also to find the significant risk factors that help to predict the recurrence of dislocation in first-time dislocators.


This is a comparison study between 50 normal individuals as a control population (group-1) and 94 patients with patellar instability done between 2013 and 2017. Further, 94 patients (group-2) were divided into first-time dislocators (group-2A) and recurrent dislocators (group-2B) which include 39 and 55 patients, respectively. Demographic factors like age, sex, the age of the first dislocation, mechanism of injury, and laterality and MRI risk factors like trochlear dysplasia, patellar height, patellar malalignment, and lateralization of tibial tuberosity were statistically analyzed.


All parameters used to measure each MRI factors showed significant difference with p value < 0.0001 between group 1 and group 2 except PTI (0.035) and TT-PCL (0.036). While comparing demographic factors between first-time dislocators and recurrent dislocator groups, patients with first-time dislocation < 16 years of age (OR-3.6) and bilateral involvement are associated with recurrence and among MRI factors, trochlear dysplasia (odds ratio OR-12), patellar tilt (OR-0.2), and patella alta (OR-4.9) were known to be associated with higher chance of recurrence.


There is a significant difference in anatomic risk factors between normal and patellar instability knees. PTI and TT-PCL are less significant than the previous parameters. Age < 16 years, the presence of trochlear dysplasia, patella alta, and bilateral involvement have a significant role as prediction factors in a recurrent dislocation in both adolescents and adults.

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Correspondence to Rajagopalakrishnan Ramakanth.

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Sundararajan, S.R., Raj, M., Ramakanth, R. et al. Prediction of recurrence based on the patellofemoral morphological profile and demographic factors in first-time and recurrent dislocators. International Orthopaedics (SICOT) (2020).

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  • Patellofemoral morphology
  • First-time Patellar dislocators
  • Recurrent Patellar dislocators